The purpose of this study is to develop and validate indices of patient health status/outcome for eventual use in measurement of paramedic performance. The unit of analysis is the prehospital status/outcome of patients with nontraumatic chest pain. The four indices are (1) the momentary severity index, (2) the stability/instability index, (3) the criticality index, and (4) the probability prognostic index (given no treatment). (The last index is not to be validated for this project.) Two principal forms of index validation will be used: congruent and predictive. The criterion for estimating predictive validity is care intensity provided by personnel in the prehospital (paramedics) and inhospital settings.